I am having some issues I can't seem to solve with my G4. Just last night I tried to charge the laptop and it said it was running off of batteries - while the orange light was on. It just ran down the battery and died.

I brought it to a mac store to try different batteries and different power adapters - my mac failed to charge a different (confirmed working) battery, and also couldnt use a different power adapter. This indicates that the issue is not the power adapter or the battery.

I think my laptop has something wrong inside it - I didn't drop it, so I don't know how something could have broke in the hardware.

I have also tried to do a power management module by taking out the AC power and the battery, then holding down the power button. No luck :(

Sounds like your power board has gone south. The power
board on my Lombard went bad and I've never dropped it
either. I found out after tearing it down the power in adapter
on the board had come unsoldered, a quick fix in my case.
Check out ifixit.com for step by step instructions on how to
tear down your powerbook if you're feeling up to it. If you
have AppleCare still on it, I'd send it in for repair as
dismantling the machine yourself will void the warranty.